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The bond test may fail due to the excessive length of the equipment supply cord. Extension leads may also fail due to increased resistance
induced by long cable lengths. When a bond test fails the PAT400 will display a lead compensation table, allowing the pass limit to be
modified. See section 3.11 and Appendix A.6 for further details on lead compensation.
A.2 Insulation testing
This is used to confirm there is separation between the live conductors (live and neutral) and any accessible conductive parts.
The instrument will short together the live and neutral conductors and then apply a 500 V or 250 V insulation test between the
temporarily connected live/neutral and the earth.
Typically a test voltage of 500 V is used. However on sensitive equipment or especially where there are surge protection devices fitted, a
250 V option is available.
For Equipment with no return earth (Class II) the use of an external probe is required to provide the return.
In situ testing
In situ insulation testing is not possible on the PAT400. However, the Touch Leakage test can be used in the same situation as the In situ
Bond test in Section A1(iii) above, as an alternative to the insulation test.
A.3 Leakage testing
(i) Differential earth leakage test (IDIFF).
Also called protective conductor current
Test voltage: 230 Vac 50 Hz →19.99 mA
110 Vac 50 Hz →19.99 mA (UK models only)
The differential earth leakage test determines whether any current is flowing to earth. Normally appliances should have no, or very little,
earth leakage current. Class 2 (double insulated appliances) could exhibit earth leakage through its mountings or by operator contact.
During the test the actual mains voltage is also measured at the appliance socket. In order to ensure that the equipment is safe even
when the mains supply rises to its maximum permitted value (253 V or 121 V) the PAT calculates and displays the leakage current that
would flow at this value.
Warning: A differential test will operate the asset during the test. Make sure the asset is well secured before the test
scommences.
(ii) Substitute leakage test (IPE).
Also called alternative earth leakage
Also called equivalent earth leakage
Test voltage: 40 Vac 50 Hz → 19.99 mA
For this test the appliance has its phase conductors joined together within the PAT and a 40 V supply is applied between both phase
conductors and the protective conductor connection of the equipment under test in the case of Class 1 equipment. In the case of Class 2
appliances the test lead and probe is connected to the PAT.
This probe is applied to any conductive parts on the appliance under test. The actual voltage is measured at the appliance socket. From
these readings the earth leakage current of the appliance is calculated and scaled depending upon appliance supply voltage
(253 V or 121 V).
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